Hi Bharath, Thanks for taking the time to try to fix this report. However, this doesn't look right. On Fri, 2019-08-16 at 23:30 +0530, Bharath Vedartham wrote: > This patch fixes a memory leak bug reported by syzbot. Link to the > bug is given at [1]. > > A local variable name is used to hold the copied user buffer string > using strndup_user. strndup_user allocates memory using > kmalloc_track_caller in memdup_user. This kmalloc allocation needs to be > followed by a kfree. > > This patch has been tested by a compile test. > > [1] https://syzkaller.appspot.com/bug?id=ce692a3aa13e00e335e090be7846c6eb60ddff7a > > Reported-by: syzbot+b2098bc44728a4efb3e9@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx> > --- > drivers/dma-buf/dma-buf.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index f45bfb2..9798f6d 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -342,6 +342,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) > } > kfree(dmabuf->name); > dmabuf->name = name; > + kfree(name); > Just by looking at this, you can deduce something is not right. You are assigning "name" to dmabuf->name, but then releasing "name"! So now, dmabuf->name has free memory, which will lead to user-after-free issues. Note also, that this function doesn't look leaky since the previous "name" is freed, before setting a new one. Maybe the syzbot report is some kind of false positive? Also, I _strongly_ suggest that in the future you don't compile-test only these kind of not trivial fixes. Since you are touching a crucial part of the kernel here, you should really be testing properly. Specially since syzbot produces a reproducer. Consider compile test as something you do when your changes are only cosmetic, and you are completely and absolutely sure things will be OK. Thanks. Ezequiel
